Dark Spots on CRT

[HallelujahJaffar]

I have a Magnavox MS274504/17 that I love but I’ve got some shadowy areas on the left and right side of the screen. Almost like a bit of a circle that’s showing on left and right edge. Left edge/upper left is worse. Most visible on white background, but most solid color backgrounds show it to some degree.

Here are some pics (Imgur seems slow to load lately so sorry if link doesn’t work right away)

https://imgur.com/gallery/dark-spots-crt-tv-28Fb3W3

I don’t think it’s purity because it’s visible regardless of test screen color (white, red, blue or green) and someone suggested maybe focus, but adjusting the Pot didn’t make it any better or worse.

Anyone have any guesses? I did test quick with a magnet on back of tube with case off and it seemed to help so considered maybe some well placed weak fridge magnets inside, but thinking it may not be best solution or could make it worse.

I have a second CRT (Sanyo DS24425) but the Magnavox is much better picture quality and preferred for 16-bit gaming. I just repaired a cracked solder point to on the AV board to fix a speaker that went out and if I could fix this the set would be perfect.

There is a service manual listed but I can’t find anything that sticks out.

[Josh128]

Very interesting, looks like it affects green more than anything else, almost not present on full red. Its possible that its burn in.

How are white horizontal lines in the problem area? Are they pure white, how is the horizontal and vertical convergence in the problem areas?

[HallelujahJaffar]

Very interesting, looks like it affects green more than anything else, almost not present on full red. Its possible that its burn in.

How are white horizontal lines in the problem area? Are they pure white, how is the horizontal and vertical convergence in the problem areas?

It’s strange - everything seems and looks totally fine except for these shadowy areas. I opened it up again to take a look and did find that holding something magnetic about 6” behind the tube on the left solids seems to get rid of it completely, without causing any real impact to the grid.
The red might be the photos I took, as it’s apparently on al colors.

Not sure if a yoke adjustment might improve things (doubt it based on what I’ve researched but not an expert) or if there is a way I can find the right strength magnet that I could place on rear of tube somewhere to eliminate it. I keep wondering if the magnets around the yoke deflector maybe got moved or something. The shape of the shadows (almost a lens effect or curved) is throwing me for a loop

Worst case I try to sell the TV cheap. Just bummer because I really want a set without issues and people in my area are making crazy prices - $300 for a Trinitron

[Josh128]

If its helped by mags, its a localized purity issue. Could be a missing mag or also be some kind of sag or partial detachment/bowing of the shadow mask in that area. This is a shadow mask, not aperture grille type CRT, no?

Dont touch the yoke if everything else is OK. Get you some mini 1 to 1.5mm thick, 1cm diameter round or rectangular neodymium magnets, some double sided "Alien style tape" , and place the mag on the back of the tube, close it up, and never look back. If a magnet fixes it, 100% go that route and dont blink an eye.

[Syntax]

Turn the display on, rotate it while on, does the issue move or change?